It has already been proposed, in French application No. 69/23972 of July 15, 1969, now French Pat. No. 2,053,681 of Apr. 16, 1971 that the powder charge of such hot gas generators be constituted by a plurality of lamellae of powder disposed side by side and fixed by a continuous peripheral zone to a common support (hereinafter called "shoe ), which arrangement simultaneously ensures a predetermined relative positioning of the said lamellae with respect to each other, the imparting to the charge assembly of the character of a single block, and the fixing of the charge thus constituted to the combustion chamber wall of the hot gas generator.
However, this earlier solution has not yielded entire satisfaction for certain uses, because it requires, for the anchoring of each lamella to the common shoe, a continuous fixation zone along which a continuous marginal strip (of no inconsiderable width) of the lamella in question will be embedded in the body of the shoe.
This arrangement entails the drawback of subtracting from the normal combustion process all this marginal strip embedded in the shoe, and at the end of combustion considerable residues remain (in shop jargon called "leftover plugs" or "leftover carrots") that escape the normal combustion process and continue to burn, emitting tongues of flame and smoke prejudicial to the concealment of mechanisms equipped with such hot gas generators. Moreover, the continuity of the lamella fixation zone forms, at the level of the implantation of such lamellae, a kind of barrier that prevents any communication between the compartments defined by said lamellae, which impedes the balancing of pressures there, reduces combustion output, and causes risk of rupture or tearing in the implantation zones of the said lamellae.
The invention is intended to obviate these drawbacks of hot gas generators with a one-piece lamellar powder charge, whereof the lamellae are implanted in a common shoe along a continuous marginal zone of fixation.
The invention thus relates to the development of a hot gas generator with lamellar powder charge, in which on the one hand the portion of the lamellae outside the normal process of combustion is less, and wherein on the other hand there is, upon firing of the charge, an almost instantaneous balancing of pressures between the various compartments defined by the said lamellae.
The powder hot gas generator of the invention comprises a one-piece lamellar powder charge, constituted by a plurality of lamellae of powder disposed side by side, regularly spaced, and fixed to a common shoe that ensures the relative positioning of the said lamellae with reference to each other, allowing fixation of the one-piece charge thus constituted to the combustion chamber wall of the hot gas generator, said generator being characterized in that each lamella comprises, in its marginal zone along which it is fixed to the common shoe, anchoring teeth embedded over only part of their height in the said shoe, so that between any two successive teeth of the same lamella there will be an aperture constituting a communication between the spaces on either side of the said lamella.
Because of this arrangement, there is on the one hand reduction to the minimum of the portion of the powder lamellae that does not participate in the normal combustion process, which portion is solely limited to the embedded parts of the lamella anchoring teeth, and on the other hand because of the apertures in question, it is possible to effect communication between the various compartments separating the successive lamellae, which communication allows a balancing of pressures between said compartments from the beginning of the combustion resulting in an increase in combustion yield and better mechanical resistance of the one-piece powder charge unit to the dynamic forces of the gases.
It is well to note, to avoid any ambiguity in the matter of the term "lamella," that this term designates thin flat elements, advantageously between a few tenths of a millimeter and a few millimeters, the contour of the lamellae generally but not necessarily being quadrangular, especially rectangular.
In this case, i.e., in the case of rectangular lamellae, the width or height is preferably between 5 and 50 mm.
The anchoring teeth of the lamellae then advantageously have a height and length that is between one tenth and one third of the width of said lamellae.
As to the number of anchoring teeth provided along the marginal fixation zone of each lamella, this is obviously a function, among other parameters, of the length of the said fixation zone, but it seems that the anchoring teeth in question may advantageously be provided, within the dimensional ranges preferentially indicated above for the lamellae and their anchoring teeth, in a proportion of one tooth for every 2 to 6 centimeters along the marginal fixation zone.
In the above described case of rectangular lamellae, the marginal fixation zone will be along the large side of the lamellae.
In any case, the depth of implantation of the anchoring teeth in the fixation shoe is preferably between one quarter and three quarters of the height of said teeth, said implantation depth being advantageously of the order of half the height of the teeth.
As used herein, the width or height of, for instance, a rectangular lamella is the dimension of the main rectangular portion, measured normally to the shoe or mat, and the length is measured normally to the width or height. The height and length measurements of the anchoring teeth are measured as indicated in FIG. 2 of the drawings.
As far then as the shoe that serves as support for such a lamellar charge is concerned, it is preferably made of flexible polymerizable plastic, advantageously of the silicone family, such a shoe then preventing the advantage of being readily adaptable to the combustion chamber wall and of lending itself to an advantageous anchoring process, which will be more explicitly described below.
In this matter, preferably a "flat" manufacturing process is chosen, which leads to production of a blank that enters into the framework of the invention and that is presented as a kind of lamellar mat, whereof one of the faces is constituted by the outer portion of the shoe and the other by the outer portion of the powder lamellae, disposed parallel to one another.
It is then possible to cut from this lamellar mat, pieces that correspond to the developed surface of the finished charge, and then if necessary adapt these pieces to the geometric characteristics of the combustion chamber wall on which the lamellar powder charge is to be fixed, e.g. by adhesion.
Thus, in the case of a cylindrical combustion chamber whose side wall may receive a lamellar powder charge, a rectangular or square blank will be cut from the mat, one of the dimensions corresponding to the length of the charge and the other to the external circumference, said blank then being rolled to a cylindrical configuration.
The process of the invention for the manufacture, starting with a mat of a lamellar powder charge whereof the lamellae are anchored in the shoe by means of teeth provided along the marginal fixation zone of each lamella, is characterized by the following successive stages:
provisional fixation on a first plate, of sheets of toothed powder lamellae disposed in parallel and adjacent, or separated from one another;
spreading on a second plate, of a layer (possibly reinforced with glass fabric) of polymerizable plastic material, said layer being intended to constitute the charge shoe;
before polymerization of said layer is completed, putting said first and second plates in a mounting arrangement so designed that the teeth of the lamellae will be partly embedded in the shoe in the course of polymerization;
completion of the polymerization of the shoe;
removal of the two plates, the shoe then enclosing the teeth of the powder lamellae (partly embedded teeth);
cutting out the lamellar charge thus prepared;
shaping the said charge, if necessary, for its adaptation in the combustion chamber of the hot gas generator.